Not correctly estimated mind you
It's so wrong that an estimate of zero deaths would certainly be considerably less wrong.
(to put this into context, there have probably not been 800 million deaths in all wars combined, and as has been noted, scholars estimate that maybe 6-9% of all wars have been primarily religious, with % death toll likely lower than this)
Lists like this are not scholarly but derivative of some post on reddit years back made by some random punter on the internet.
This list probably overstates religious deaths by 150 million (only on the ones with attached casualty figures). Other than the numbers often being an order of magnitude too high, some of these links to 'religious' are ludicrously tenuous.
For example:
"AIDS deaths in Africa largely due to opposition to condoms" this is total nonsense, compare HIV rates in Protestant and Catholic Africa if you don't believe
Muslim Conquests of India: 80,000,000: All casualty figures for all historical conflicts tend to be vastly overstated, this is one of the most egregious. Were it true, one would have to believe that a conflict of greater intensity than the 30 Years War waged for centuries and at the end of the 'greatest genocide in history' there were more Hindus than at the start of it and the country was far richer. (also the decision not to include many of these deaths as being part of the, purportedly 'not religious', Mongol conquests is pretty arbitrary really)
Even the more plausible ones like the 30 Years War are far more nuanced. it had some religious dimension, but was more about territory and the power rivalry. It would have been less than half as long if Sweden hadn't joined in to carve out some more territory. The Protestant Swedes were assisted by the Catholic French in this endeavour which shows that religion wasn't exactly the overriding concern. Or the fact that for the Dutch it was really part of the 80 Years War for independence.